Determine the effect changing the object to the lens distance has on the distance at which the image is displayed.

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Introduction

Lenses

Aim:

To determine the effect changing the object to the lens distance has on the distance at which the image is displayed

Prediction:

To make my predictions I decided to use a quantitive prediction method, the equation for this is:

1 = 1 + 1

focal length (cm) Object-lens distance Lens-image distance

To use this method I will have to know the focal length of the lens. To do this we did a preliminary experiment where I put a lens opposite a window with a piece of paper behind. I moved the paper back and forth until the image of the outside became clear on the paper. The distance from the lens to the card, when the image is in focus gives the focal length.

Despite this the chance for inaccuracies, the investigation turned up no anomalies and the quality of the evidence is good. But the experiment could be repeated with better equipment (mentioned above) and a wider range of lengths. I could also repeat the experiment varying the angle of the lens, and the focal length of the lens to see if they have an effect on the images produced and if so, what the effects are.

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This could divide the human error by about ten. If I could repeat the test I would test the affect of voltage on the efficiency, and I would use one set number of weights. This test would probably show us a decrease in efficiency as the voltage is increased.

These were the range of the focal point because I could not find the specific focal point with my eye, measuring the meter rule or tape measurer, estimating where the lens was because the lens holder obscured the vision of the meter rule.

The preliminary investigations also determine the focal length of what lens I will have chosen. The light intensity will stay at 12V; it means the image is clearer and easily seen. The window simulates the object, which will be much brighter in front of the lamp, making the image produced easier to be seen.

of working out the magnification I have got virtually the same results, which show the same trend that proves the hypothesis, moving the object further away from the focal point of a converging lens will decrease the magnification of the size of the image.

The exact position of the light filament was not sure, nor was that of the lens, with a more accurate way of measuring this (perhaps with a different object to measure other than a light bulb) the difference could have been a few millimeters which would definitely have increased the precision of the experiment.

This is a virtual focal point. Because of this, a convex lens can be used to project an image onto a screen, the sort that would be used in a cinema projector, forming a "real image" which can be seen.

Activity 23 Apparatus Set-up (1) As the object-lens distance (u) and the lens-image distance (v) i.e. the lens-screen distance were altered, some interesting things happened. * The red and blue light are flipped vertically (upside-down). This can be explained through the use of a ray diagram as seen on Pg 2.